The facility, located in Ponders End in north London, includes compound and bulk manufacturing units producing a number of MSD's products and has the capacity to produce 300 tons of products per year.
The acquisition is the next step in Aesica's ambition to become a leading supplier of active pharmaceutical ingredients (APIs).
Under the terms of the deal, Aesica will also supply intermediates and APIs to Merck over a number of years, which represents a potential revenue stream of between $150m (€118m) and $300m, said the firm.
"Through the acquisition, we gain a significant increase in our manufacturing capacity and capabilities, as well as a highly valued client via the supply agreement with Merck," said Robert Hardy, Aesica CEO.
"Buying Ponders End is an important part of our strategy to build on our leading position in the supply of APIs through the acquisition of products and facilities, and through growing our custom synthesis business."
For Merck, the sale of the site is part of the firm's global restructuring of its manufacturing network that began last November, aimed at reducing the company's cost structure, increasing efficiency, and enhancing competitiveness.
"This sale is part of our strategy to create a leaner, more efficient manufacturing network to meet our supply demand for the next few years," a Merck spokesperson told In-pharmaTechnologist.com.
However, the New Jersey drugmaker has also made some large investments in facilities in recent months. The company, who saw its materials and production costs jump 25 per cent for the second quarter of 2006, has recently invested $300m in a new North Carolina facility, which it sees as an opportunity to introduce efficiencies and cut waste.
The firm has also recently invested $100m to expand its manufacturing plant in Singapore, bringing the drug giant's investment in this region to over S$1bn.